Reiko Kobayakawa

Osaka Bioscience Institute · Department of functional neuroscience

The mammalian olfactory system mediates various responses, including aversive behaviours to spoiled foods and fear responses to predator odours. In the olfactory bulb, each glomerulus represents a single species of odorant receptor. Because a single odorant can interact with several different receptor species, the odour information received in the...

Significance It is now widely accepted that the range of pheromones that control social behaviors are processed by both the vomeronasal system (VNS) and the main olfactory system (MOS). However, the functional contributions of each subsystem in social behavior remain unclear. Here, we showed that mice with loss-of-function confined to the dorsal MO...

Fear is induced by innate and learned mechanisms involving separate pathways. Here, we used an olfactory-mediated innate-fear versus learned-fear paradigm to investigate how these pathways are integrated. Notably, prior presentation of innate-fear stimuli inhibited learned-freezing response, but not vice versa. Whole-brain mapping and pharmacologic...

In developing brains, activity-dependent remodeling facilitates the formation of precise neuronal connectivity. Synaptic competition is known to facilitate synapse elimination; however, it has remained unknown how different synapses compete with one another within a post-synaptic cell. Here, we investigate how a mitral cell in the mouse olfactory b...

Recent long-term optical imaging studies have demonstrated that the activity levels of hippocampal neurons in a familiar environment change on a daily to weekly basis. However, it is unclear whether there is any time-invariant property in the cells' neural representations. In this study, using miniature fluorescence microscopy, we measured the neur...

Hibernation or torpor are energy-saving strategy in some thermostatic animals to survive harsh environments such as extreme cold and starvation. The ability to induce such hypometabolic states has garnered considerable interest due to its potential medical benefits. However, the mechanisms regulate these hypometabolic state remain largely unknown....

We hypothesized that circulatory and jejunal mucosal blood flow would improve after 2-methyl-2thiazoline (2MT) administration in endotoxic shock. This study aimed to evaluate changes in systemic circulation and in superior mesenteric venous (SMV) blood flow and jejunal mucosal tissue blood flow of the intestinal vascular system over time after admi...

Sensory signals are critical to perform adaptive social behavior. During copulation, male mice emit ultrasonic vocalizations (USVs). Our previous studies have shown that female mice exhibit approach behavior toward sound sources of male USVs and that, after being exposed to a male pheromone, exocrine gland-secreting peptide 1 (ESP1), female mice ex...

Recent long-term optical imaging studies have demonstrated that the activity levels of hippocampal neurons in a familiar environment change on a daily to weekly basis. However, it is unclear whether there is any time-invariant property in the cells’ neural representations. In this study, using miniature fluorescence microscopy, we measured the neur...

Aims: Cardiac ischaemia/reperfusion (I/R) injury remains a critical issue in the therapeutic management of ischaemic heart failure. Although mild hypothermia has a protective effect on cardiac I/R injury, more rapid and safe methods that can obtain similar results to hypothermia therapy are required. 2-Methyl-2-thiazoline (2MT), an innate fear ind...

The neural mechanisms of fear-associated thermoregulation remain unclear. Innate fear odor 2-methyl-2-thiazoline (2MT) elicits rapid hypothermia and elevated tail temperature, indicative of vasodilation-induced heat dissipation, in wild-type mice, but not in mice lacking Trpa1–the chemosensor for 2MT. Here we report that Trpa1 −/− mice show diminis...

Thiazoline-related innate fear-eliciting compounds (tFOs) orchestrate hypothermia, hypometabolism, and anti-hypoxia, which enable survival in lethal hypoxic conditions. Here, we show that most of these effects are severely attenuated in transient receptor potential ankyrin 1 ( Trpa1 ) knockout mice. TFO-induced hypothermia involves the Trpa1 -media...

Innate fear intimately connects to the life preservation in crises, although this relationships is not fully understood. Here, we report that presentation of a supernormal innate fear inducer 2-methyl-2-thiazoline (2MT), but not learned fear stimuli, induced robust systemic hypothermia/hypometabolism and suppressed aerobic metabolism via phosphoryl...

Miniaturized fluorescence microscopes are becoming more important for deciphering the neural codes underlying various brain functions. Using gradient index (GRIN) lenses, these devices enable the recording of neuronal activity in deep brain structures. However, to minimize any damage to brain tissue and local circuits, the diameter of the GRIN lens...

Mammals normally maintain a constant body temperature irrespective of their environmental temperature. However, emotions such as fear can trigger acute changes in body temperature accompanying defensive behaviors to enhance survival in life-threatening conditions. The neural mechanisms of fear-associated thermoregulation remain unclear. Here, we fi...

Therapeutic hypothermia protects the brain after cardiopulmonary arrest. Innate fear has evolved to orchestrate protective effects in life-threatening situations. Thus, strong fear perception may induce a specialized life-protective metabolism based on hypothermia/hypometabolism; however, such phenomena and their inducers are yet to be elucidated....

In the mouse olfactory bulb, sensory information detected by ~1,000 types of olfactory sensory neurons (OSNs) is represented by the glomerular map. The second-order neurons, mitral and tufted cells, connect a single primary dendrite to one glomerulus. This forms discrete connectivity between the ~1,000 types of input and output neurons. It has rema...

Innate behaviors are genetically encoded, but their underlying molecular mechanisms remain largely unknown. Predator odor 2,4,5-trimethyl-3-thiazoline (TMT) and its potent analog 2-methyl-2-thiazoline (2MT) are believed to activate specific odorant receptors to elicit innate fear/defensive behaviors in naive mice. Here, we conduct a large-scale rec...

Tables and Figure Legends Fig. S1. Initial training of wild-type (WT) and ΔD mice for odour discrimination. (A), %Correct of WT mice (black closed circles). (B), %Correct of ΔD mice (red open squares) that genetically lost all dorsal olfactory receptors. Two alternative forced choice assays with target vs. non-target odorus were performed in a Y-ma...

Similar to fingerprints, humans have unique, genetically determined body odours. In case of urine, the odour can change due to variations in diet as well as upon infection or tumour formation. We investigated the use of mice in a manner similar to “sniffer dogs” to detect changes in urine odour in patients with bladder cancer. We measured the odour...

Chemical Senses 41(9):E139-E139(2016), abstract of ISOT2016 poster presentation

Pairs of enantiomeric odor ligands are difficult to resolve by instrumental analyses because compounds with mirror-image molecular structures have almost identical physicochemical properties. The olfactory system, however, discriminates ( – )-forms of enantiomers from their (+)-forms within seconds. To investigate key olfactory receptors for enanti...

Enantiomeric pairs of mirror-image molecular structures are difficult to resolve by instrumental analyses. The human olfactory system, however, discriminates (-)-wine lactone from its (+)-form rapidly within seconds. To gain insight into receptor coding of enantiomers, we compared behavioural detection and discrimination thresholds of wild-type mic...

Odor signals are conveyed from the olfactory bulb to the olfactory cortex (OC) by mitral cells (MCs) and tufted cells (TCs). However, whether and how the two types of projection neuron differ in function and axonal connectivity is still poorly understood. Odor responses and axonal projection patterns were compared between MCs and TCs in mice by vis...

Granule cells (GCs) in the mouse olfactory bulb (OB) continue to be generated in adulthood, with nearly half incorporated and the remainder eliminated. Here, we show that elimination of adult-born GCs is promoted during a short time window in the postprandial period. Under restricted feeding, the number of apoptotic GCs specifically increased withi...

Various social behaviours in mice are regulated by chemical signals called pheromones that act through the vomeronasal system. Exocrine gland-secreting peptide 1 (ESP1) is a 7-kDa peptide that is released into male tear fluids and stimulates vomeronasal sensory neurons in female mice. Here, we describe the molecular and neural mechanisms that are i...

Mapping the Neuronal Map In vertebrates, sensory information is topographically represented as a neural map in the brain. How is the neural map formed in the brain? Nearly a half-century ago, Roger Sperry proposed the “chemoaffinity” model, in which the positional cues on the target determine the axonal projection site, thereby establishing the top...